Resveratrol is a major phytoalexin produced by plants in response to various stresses and promotes disease resistance. The resistance of North American grapevine Vitis rupestris is correlated with a hypersensitive reaction (HR), while susceptible European Vitis vinifera cv. ‘Pinot Noir’ does not exhibit HR, but expresses basal defence. We have shown previously that in cell lines derived from the two Vitis species, the bacterial effector Harpin induced a rapid and sensitive accumulation of stilbene synthase (StSy) transcripts, followed by massive cell death in V. rupestris. In the present work, we analysed the function of the phytoalexin resveratrol, the product of StSy. We found that cv. ‘Pinot Noir’ accumulated low resveratrol and its glycoside trans-piceid, whereas V. rupestris produced massive trans-resveratrol and the toxic oxidative δ-viniferin, indicating that the preferred metabolitism of resveratrol plays role in Vitis resistance. Cellular responses to resveratrol included rapid alkalinisation, accumulation of pathogenesis-related protein 5 (PR5) transcripts, oxidative burst, actin bundling, and cell death. Microtubule disruption and induction of StSy were triggered by Harpin, but not by resveratrol. Whereas most responses proceeded with different amplitude for the two cell lines, the accumulation of resveratrol, and the competence for resveratrol-induced oxidative burst differed in quality. The data lead to a model, where resveratrol, in addition to its classical role as antimicrobial phytoalexin, represents an important regulator for initiation of HR-related cell death.

The great potential of pharmacologically active secondary plant metabolites is often limited by low yield and availability of the producing plant. Chemical synthesis of these complex compounds is often too expensive. Plant cell fermentation offers an alternative strategy to overcome these limitations. However, production in batch cell cultures remains often inefficient. One reason might be the fact that different cell types have to interact for metabolite maturation, which is poorly mimicked in suspension cell lines. Using alkaloid metabolism of tobacco, we explore an alternative strategy, where the metabolic interactions of different cell types in a plant tissue are technically mimicked based on different plant-cell based metabolic modules. In this study, we simulate the interaction found between the nicotine secreting cells of the root and the nicotine-converting cells of the senescent leaf, generating the target compound nornicotine in the model cell line tobacco BY-2. When the nicotine demethylase NtomCYP82E4 was overexpressed in tobacco BY-2 cells, nornicotine synthesis was triggered, but only to a minor extent. However, we show here that we can improve the production of nornicotine in this cell line by feeding the precursor, nicotine. Engineering of another cell line overexpressing the key enzyme NtabMPO1 allows to stimulate accumulation and secretion of this precursor. We show that the nornicotine production of NtomCYP82E4 cells can be significantly stimulated by feeding conditioned medium from NtabMPO1 overexpressors without any negative effect on the physiology of the cells. Co-cultivation of NtomCYP82E4 with NtabMPO1 stimulated nornicotine accumulation even further, demonstrating that the physical presence of cells was superior to just feeding the conditioned medium collected from the same cells. These results provide a proof of concept that combination of different metabolic modules can improve the productivity for target compounds in plant cell fermentation.

. Crop wild relatives as genetic resources Á the case of the European wild grape. Can. J. Plant Sci. 95: 905Á912. Vitis vinifera L. ssp. sylvestris (Gmelin) Hegi, the European Wild Grape and ancestor of cultivated grapevine varieties (V. vinifera L. ssp. vinifera) is the sole wild grapevine species existing in Europe. This important crop wild relative (CWR) species is almost extinct, and persists only in residual habitats. Since these habitats are close to vineyards, this CWR species is endangered by hybridisation with its descendant crop and naturalised rootstocks that originate from viticulture. For this reason, we addressed two questions: To what extent have the remaining South German European Wild Grape accessions escaped hybridisation and preserved genetic identity? Second, what is the potential of this CWR species as a genetic resource for breeding in relation to several grapevine diseases? Using a set of highly resolving genetic markers, we were able to exclude introgression of autochthonous sylvestris accessions by cultivated grapevine. However, we detected introgression mostly from wild American species used as rootstocks in viticulture. The autochthonous accessions can be grouped into clusters. Comparative inoculation studies with the grapevine pathogens powdery mildew (Erysiphe necator), downy mildew (Plasmopara viticola), and black rot (Guignardia bidwellii) revealed relatively high levels of resistance in some of the ssp. sylvestris accessions and represents a valuable genetic resource for resistance breeding.Key words: European wild grape, Vitis sylvestris, crop wild relative, Erysiphe necator, Plasmopara viticola, Guignardia bidwellii Schro¨der, S., Kortekamp, A., Heene, E., Daumann, J., Valea, I. et Nick, P. 2015. Les espe`ces sauvages apparente´es aux cultures en tant que ressource ge´ne´tique Á cas du raisin sauvage europe´en. Can. J. Plant Sci. 95: 905Á912. Vitis vinifera L. ssp. sylvestris (Gmelin) Hegi, le raisin sauvage europe´en, anceˆtre de toutes les varie´te´s de vigne (V. vinifera L. ssp. vinifera) cultive´es, est la seule vigne sauvage qui existe en Europe. Cette importante espe`ce sauvage apparente´e a`la vigne cultive´e est presque e´teinte, et on ne la retrouve que dans des habitats re´siduels voisins des vignobles. L'hybridation avec la descendance et les porte-greffes naturalise´s issus de la viticulture menace l'espe`ce sauvage d'extinction. C'est pourquoi les auteurs se sont pose´deux questions : dans quelle mesure les obtentions de raisin sauvage europe´en du sud de l'Allemagne ont-elles e´chappeá`l 'hybridation et pre´serve´leur identite´ge´ne´tique, et quel potentiel cette ESA pre´sente-t-elle en tant que ressource ge´ne´tique pour l'hybridation, face a`diverses maladies de la vigne? En recourant a`un jeu de marqueurs ge´ne´tiques a`haute re´solution, les chercheurs sont parvenus a`exclure les introgressions venant de la vigne cultive´e des obtentions indige`nes de sylvestris. Ils ont ne´anmoins de´cele´des introgressions venant essentiellement des espe`ces ame´ricaines empl...